Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/004—Photosensitive materials
  • G03F7/075—Silicon-containing compounds
  • G03F7/0757—Macromolecular compounds containing Si-O, Si-C or Si-N bonds
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/0005—Production of optical devices or components in so far as characterised by the lithographic processes or materials used therefor
  • G03F7/001—Phase modulating patterns, e.g. refractive index patterns
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/004—Photosensitive materials
  • G03F7/075—Silicon-containing compounds
  • G03F7/0755—Non-macromolecular compounds containing Si-O, Si-C or Si-N bonds
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
  • G03H1/02—Details of features involved during the holographic process; Replication of holograms without interference recording
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
  • G11B7/0065—Recording, reproducing or erasing by using optical interference patterns, e.g. holograms
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
  • G11B7/2403—Layers; Shape, structure or physical properties thereof
  • G11B7/24035—Recording layers
  • G11B7/24044—Recording layers for storing optical interference patterns, e.g. holograms; for storing data in three dimensions [3D], e.g. volume storage
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
  • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
  • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
  • G11B7/244—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
  • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
  • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
  • G11B7/244—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only
  • G11B7/245—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only containing a polymeric component
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
  • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
  • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
  • G11B7/244—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only
  • G11B7/25—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only containing liquid crystals
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11C—STATIC STORES
  • G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
  • G11C13/04—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using optical elements ; using other beam accessed elements, e.g. electron or ion beam
  • G11C13/042—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using optical elements ; using other beam accessed elements, e.g. electron or ion beam using information stored in the form of interference pattern
• • G—PHYSICS
  • G02—OPTICS
  • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
  • G02C2202/00—Generic optical aspects applicable to one or more of the subgroups of G02C7/00
  • G02C2202/14—Photorefractive lens material
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
  • G03H1/02—Details of features involved during the holographic process; Replication of holograms without interference recording
  • G03H2001/026—Recording materials or recording processes
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
  • G03H1/02—Details of features involved during the holographic process; Replication of holograms without interference recording
  • G03H2001/026—Recording materials or recording processes
  • G03H2001/0264—Organic recording material
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H2260/00—Recording materials or recording processes
  • G03H2260/12—Photopolymer
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H2260/00—Recording materials or recording processes
  • G03H2260/50—Reactivity or recording processes
  • G03H2260/54—Photorefractive reactivity wherein light induces photo-generation, redistribution and trapping of charges then a modification of refractive index, e.g. photorefractive polymer
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H2270/00—Substrate bearing the hologram
  • G03H2270/53—Recording material dispersed into porous substrate

Definitions

• This invention relates generally to photo-induced refractive media for holographic data storage; and more particularly to a photo-induced refractive polymeric composition for use as a high-density storage medium for optically based data storage devices.
• BACKGROUND Optical systems provide extremely fast and effective means for processing information.
• an image comprising data is modulated into a coherent light beam. This can be performed by a spatial light modulator placed in the beam. The resulting spatially modulated beam then enters a series of optical elements which filter and process the image, and a detector records the final output.
• the list of applications for these systems is long, including image and data processing, pattern recognition, optical computation, and high density data storage systems such as holographic data storage systems.
• optical data storage material should have, including: excellent optical quality, high recording fidelity, high dynamic range, low scattered light, high sensitivity, and non-volatile storage.
• High recording fidelity is important because the material must faithfully record the data beam amplitude so that this high quality image can be reconstructed when the data is read out.
• High dynamic range is important because the larger the amount of data that is recorded in a common volume of material, the weaker each bit of data becomes ; the signal strength scales as the inverse square of the amount of data, and is limited ultimately by the ability of the material to respond to optical exposure with the refractive index modulation that records the data.
• the light scattering properties of the material are important because the ultimate lower limit to the strength of optical materials that are useful for data storage is determined by noise from readout beam scattering. Thus, scattered light also limits storage density.
• High sensitivity is likewise important because to store data in the material at a reasonable data rate, the material should respond to the recording beams with high sensitivity.
• non-volatile storage is perhaps of greatest concern because the material must retain the stored data for a time consistent with a data storage application, and should do so in the presence of the light beams used to read the data.
• an irreversible material such as a photopolymer
• a reversible material is chosen in order to implement erasable/re-writable data storage, the requirement for nonvolatility is in conflict with that for high sensitivity unless a nonlinear writing scheme, such as two-color gated recording is used.
• each of these systems and compositions contains limitations that make the development of new materials for optical data storage necessary.
• the present invention is directed in part to a composition, method and system for recording or storing data by stimulating a composition having a refraction modulating composition dispersed in a polymer matrix wherein the phase contrast is purely the result of the crosslinking of the macromers followed by macromer diffusion, such that there is a null point where the volume shrinkage is overcome by the macromer diffusion.
• Applicants discovered that since there is a refractive index contrast between the matrix and the macromer, a composition comprising a refraction modulating composition dispersed in a polymer matrix can be stimulated in particular patterns and these patterns can be used for data recording and storage.
• the invention is directed to a composition for data storage comprising a first polymer matrix and a refraction modulating composition dispersed therein.
• a refraction modulating composition capable of stimulus-induced polymerization can be suitably used, such as photorefractive, photo-induce refractive, photo-addressable, and liquid crystal compositions.
• the stimulated region of the composition represents one kind of data and a non-stimulated region of the composition represents another kind of data.
• the invention is also directed to a method of recording data comprising stimulating a composition, wherein the composition comprises a first polymer matrix and a refraction modulating composition dispersed therein wherein the refraction modulating composition is capable of stimulus-induced polymerization, and wherein a stimulated region of the composition represents one kind of data and a non-stimulated region of the composition represents another kind of data.
• the invention is also directed to apparatuses for recording or storing data by stimulating a composition having a refraction modulating composition as described above, where a stimulated region of the composition represents one kind of data and a non-stimulated region of the composition represents another kind of data.
• Figure la is a schematic of a disk of the present invention being irradiated in the center followed by irradiation of the entire disk to "lock in” the data.
• Figure lb is a schematic of a disk of the present invention being irradiated in the center followed by irradiation of the entire disk to "lock in” the data.
• Figure lc is a schematic of a disk of the present invention being irradiated in the center followed by irradiation of the entire disk to "lock in” the data.
• Figure Id is a schematic of a disk of the present invention being irradiated in the center followed by irradiation of the entire disk to "lock in” the data.
• Figure 2a illustrates the prism irradiation procedure that is used to quantify the refractive index changes after being exposed to various amounts of irradiation.
• Figure 2b illustrates the prism irradiation procedure that is used to quantify the refractive index changes after being exposed to various amounts of irradiation.
• Figure 2c illustrates the prism irradiation procedure that is used to quantify the refractive index changes after being exposed to various amounts of irradiation.
• Figure 2d illustrates the prism irradiation procedure that is used to quantify the refractive index changes after being exposed to various amounts of irradiation.
• Figure 3 a shows unfiltered Moire fringe patterns of an inventive disk of the optical data storage composition.
• the angle between the two Ronchi rulings was set at 12° and the displacement distance between the first and second Moire patterns was 4.92 mm.
• Figure 3 b shows unfiltered Moire fringe patterns of an inventive disk of the optical data storage composition.
• the angle between the two Ronchi rulings was set at 12° and the displacement distance between the first and second Moire patterns was 4.92 mm.
• Figure 4 is a Ronchigram of an inventive disk of the optical data storage composition.
• the Ronchi pattern corresponds to a 2.6 mm central region of the disk.
• Figure 5a is a schematic illustrating a second mechanism whereby the formation of the second polymer matrix modulates an optical property by altering the disk shape.
• Figure 5b is a schematic illustrating a second mechanism whereby the formation of the second polymer matrix modulates an optical property by altering the disk shape.
• Figure 5 c is a schematic illustrating a second mechanism whereby the formation of the second polymer matrix modulates an optical property by altering the disk shape.
• Figure 5d is a schematic illustrating a second mechanism whereby the formation of the second polymer matrix modulates an optical property by altering the disk shape.
• Figure 6a are Ronchi interferograms of a disk of the optical data storage composition before and after laser treatment.
• Figure 6b are Ronchi interferograms of a disk of the optical data storage composition before and after laser treatment.
• Figure 7 is the corresponding Ronchi interferogram of a photopolymer film in which "CALTECH” and “CVI” were written using the 325 nm line of He:Cd laser.
• Figure 8a is a schematic of an optical data storage apparatus according to the present invention.
• Figure 8b is a schematic of an optical data storage apparatus according to the present invention.
• Figure 8c is a schematic of an optical data storage apparatus according to the present invention.
• Figure 9 is a schematic of a holographic data storage apparatus according to the present invention.
• Figure 10a is a schematic illustrating the operation of a holographic data storage system.
• Figure 10b is a schematic illustrating the operation of a holographic data storage system.
• Figure 10c is a schematic illustrating the operation of a holographic data storage system.
• Figure 1 Od is a schematic illustrating the operation of a holographic data storage system.
• Figure 11 is a photograph of a section of photopolymerized film.
• Figure 12 is a schematic of a data storage unit according to the present invention.
• the present invention relates to stimulating a composition comprising a refraction modulating composition dispersed in a polymer matrix and using stimulating patterns in data recording and storage.
• Figures la to Id illustrates one inventive embodiment of the current invention in which the refractive index of a particular disk of photo reflective material 10 is changed by light induced polymerization.
• the optical data storage element 10 comprises a first polymer modulating composition (FPMC) 12 having a refraction modulating composition (RMC) 14 dispersed therein.
• the FPMC 12 forms the optical element framework and is generally responsible for many of its material properties.
• the RMC 14 may be a single compound or a combination of compounds that is capable of stimulus-induced polymerization, preferably photo- polymerization.
• polymerization refers to a reaction wherein at least one of the components of the RMC 14 reacts to form at least one covalent or physical bond with either a like component or with a different component.
• the identities of the FPMC 12 and the RMC 14 will depend on the requirements of the end use data element 10.
• the FPMC 12 and the RMC 14 are selected such that the components that comprise the RMC 14 are capable of diffusion within the FPMC 12, e.g., a loose FPMC 12 will tend to be paired with larger RMC components 14 and a tight FPMC 12 will tend to be paired with smaller RMC 14.
• an appropriate energy source 16 e.g., heat or light
• the RMC 14 upon exposure to an appropriate energy source 16 (e.g., heat or light), the RMC 14 typically forms a second polymer matrix 18 in the exposed region 20 of the optical data storage element 10.
• the presence of the second polymer matrix 18 changes the material characteristics of this region 20 of the optical element 10 to modulate its refraction capabilities.
• the formation of the second polymer matrix 18 typically increases the refractive index of the affected region 20 of the optical data storage element 10.
• the RMC 14 in the unexposed region 22 will migrate into the exposed region 20 over time.
• the amount of RMC 14 migration into the exposed region 20 depends upon the frequency, intensity, and duration of the polymerizing stimulus and may be precisely controlled. If enough time is permitted, the RMC 14 will re- equilibrate and redistribute throughout the optical data storage element 10 (i.e., the FPMC 12, including the exposed region).
• the region is re-exposed to the energy source 16
• the RMC 14 that has since migrated into the region 20 (which may be less than if the RMC 14 were allowed to re-equilibrate) polymerizes to further increase the formation of the second polymer matrix 18.
• This process (exposure followed by an appropriate time interval to allow for diffusion) may be repeated until the exposed region 20 of the optical data storage element 10 has been sufficiently modified to store the data of interest.
• the entire data storage element 10 may then be exposed to the energy source 16 to "lock-in" the desired data by polymerizing the remaining RMC 14 that are outside the exposed region 20 before the components 14 can migrate into the exposed region 20, thus forming a read-only optical data storage element 10, as shown in Figure 1 d.
• a read-only optical data storage element 10 as shown in Figure 1 d.
• the FPMC 12 is a covalently or physically linked structure that functions as an optical data storage element 10 and is formed from a FPMC 12.
• the FPMC 12 comprises one or more monomers that upon polymerization will form the FPMC 12.
• the FPMC 12 optionally may include any number of formulation auxiliaries that modulate the polymerization reaction or improve any property of the data storage element 10.
• Suitable FPMC 12 monomers include poly-carbonates, acrylics, methacrylates, phosphazenes, siloxanes, vinyls, homopolymers, and copolymers thereof, and side chain and main chain mesogens, and photochromic and thermochromic moieties, and moieties which undergo a photo-induced cisltrans isomerization, such as, azo-benzene.
• a "monomer" refers to any unit (which may itself either be a homopolymer or copolymer) which may be linked together to form a polymer containing repeating units of the same.
• the FPMC monomer 12 is a copolymer, it may be comprised of the same type of monomers (e.g., two different siloxanes) or it may be comprised of different types of monomers (e.g., a siloxane and an acrylic).
• the one or more monomers that form the FPMC 12 are polymerized and cross-linked in the presence of the RMC 14.
• polymeric starting material that forms the FPMC 12 is cross-linked in the presence of the RMC 14.
• the RMC 14 must be compatible with and not appreciably interfere with the formation of the FPMC 12.
• the formation of the second polymer matrix 18 should also be compatible with the existing FPMC 12, such that the FPMC 12 and the second polymer matrix 18 should not phase separate and light transmission by the optical data storage element 10 should be unaffected.
• the RMC 14 may be a single component or multiple components so long as: (i) it is compatible with the formation of the FPMC 12; (ii) it remains capable of stimulus-induced polymerization after the formation of the FPMC 12; and (iii) it is freely diffusable within the FPMC 12.
• the stimulus-induced polymerization is photo-induced polymerization.
• compositions of the current invention have numerous applications in the electronics and data storage industries.
• the optical elements also have applications in the medical field, such as being used as medical lenses, particularly as IOL.
• the FPMC 12 and the RMC 14 are as described above with the additional requirement that the resulting materials be biocompatible.
• a suitable biocompatible FPMC 12 include: poly-acrylates such as poly-alkyl acrylates and poly -hydroxy alkyl acrylates; poly- methacrylates such as poly-methyl methacrylate (“PMMA”), poly-hydroxyethyl methacrylate (“PHEMA”), and poly-hydroxypropyl methacrylate (“PHPMA”); poly-vinyls suchas oly-styrene and poly-N-vinylpyrrolidone (“PNVP”); poly-siloxanes such as poly-dimethylsiloxane; poly- phosphazenes, and copolymers of thereof.
• PMMA poly-methyl methacrylate
• PHEMA poly-hydroxyethyl methacrylate
• PPMA poly-hydroxypropyl methacrylate
• poly-vinyls suchas oly-styrene and poly-N-vinylpyrrolidone
• PNVP poly-siloxanes
• Patent No.4,260,725 and patents and references cited therein provide more specific examples of suitable polymers that may be used to form the FPMC 12.
• the FPMC 12 generally possesses a relatively low glass transition temperature (“T g ”) such that the resulting optical data storage element 10 tends to exhibit fluid-like and/or elastomeric behavior, and is typically formed by crosslinking one or more polymeric starting materials wherein each polymeric starting material includes at least one crosslinkable group.
• each polymeric starting material includes terminal monomers (also referred to as endcaps) that are either the same or different from the one or more monomers that comprise the polymeric starting material but include at least one crosslinkable group, e.g., such that the terminal monomers begin and end the polymeric starting material and include at least one crosslinkable group as part of its structure.
• the mechanism for crosslinking the polymeric starting material preferably is different than the mechanism for the stimulus-induced polymerization of the components that comprise the RMC 14.
• the RMC 14 is polymerized by photo-induced polymerization, then it is preferred that the polymeric starting materials have crosslinkable groups that are polymerized by any mechanism other than photo- induced polymerization.
• polysiloxanes also known as "silicones”
• a terminal monomer which includes a crosslinkable group selected from the group consisting of acetoxy, amino, alkoxy, halide, hydroxy, and mercapto.
• silicone elements tend to be flexible and foldable, the optical data storage elements created thereby will be much less susceptible to damage and data loss.
• An example of an especially preferred polymeric starting material is bis(diacetoxymethylsilyl)-polydimethylsiloxane (which is poly-dimethylsiloxane that is endcapped with a diacetoxymethylsilyl terminal monomer).
• the RMC 14 that is used in fabricating optical data storage elements is as described above except that it has the additional requirement of biocompatibility.
• the RMC 14 is capable of stimulus-induced polymerization and may be a single component or multiple components so long as: (i) it is compatible with the formation of the FPMC 12; (ii) it remains capable of stimulus-induced polymerization after the formation of the FPMC 12; and (iii) it is freely diffusable within the FPMC 12.
• the same type of monomers that is used to form the FPMC 12 may be used as a component of the RMC 14.
• the RMC 14 monomers generally tend to be smaller (i. e. , have lower molecular weights) than the monomers which form the FPMC 12.
• the RMC 14 may include other components such as initiators and sensitizers that facilitate the formation of the second polymer matrix 18.
• the stimulus-induced polymerization is photo-polymerization.
• the one or more monomers that comprise the RMC 14 each preferably includes at least one group that is capable of photopolymerization.
• Illustrative examples of such photopolymerizable groups include but are not limited to acrylate, allyloxy, cinnamoyl, methacrylate, stibenyl, and vinyl.
• the RMC 14 includes a photoinitiator (any compound used to generate free radicals) either alone or in the presence of a sensitizer.
• Suitable photoinitiators include acetophenones (e.g., a-substituted haloacetophenones, and diethoxyacetophenone); 2,4-dichloromethyl-l,3,5-triazines; benzoin alkyl ethers; and o-benzoyloximino ketone.
• suitable sensitizers include p- (dialkylamino)aryl aldehyde; N-alkylindolylidene; and bis[p-(dialkylamino)benzylidene] ketone.
• RMC 14 monomers are poly-siloxanes endcapped with a terminal siloxane moiety that includes a photopolymerizable group.
• An illustrative representation of such a monomer is:
• Y is a siloxane which may be a monomer, a homopolymer or a copolymer formed from any number of siloxane units, and X and X 1 may be the same or different and are each independently a terminal siloxane moiety that includes a photopolymerizable group.
• Y include:
• R 1 , R 2 , R 3 , and R 4 are independently each hydrogen, alkyl (primary, secondary, tertiary, cyclo), aryl, or heteroaryl.
• R 1 , R 2 , R 3 , and R 4 are each a C C 10 alkyl or phenyl. Because RMC 14 monomers with a relatively high aryl content have been found to produce larger changes in the refractive index of the inventive lens, it is generally preferred that at least one of R 1 , R 2 , R 3 , and R 4 is an aryl, particularly phenyl.
• R 1 , R 2 , and R 3 are the same and are methyl, ethyl, or propyl and R 4 is phenyl.
• Illustrative examples of X and X 1 (or X ! and X depending on how the RMC 14 polymer is depicted) are:
• R 6 respectively where R 5 and R 6 are independently each hydrogen, alkyl, aryl, or heteroaryl; and Z is a photopolymerizable group.
• R 5 and R 6 are independently each a C r C 10 alkyl or phenyl and
• Z is a photopolymerizable group that includes a moiety selected from the group consisting of acrylate, allyloxy, cinnamoyl, methacrylate, stibenyl, and vinyl.
• R 5 and R 6 are methyl, ethyl, or propyl and Z is a photopolymerizable group that includes an acrylate or methacrylate moiety.
• an RMC 14 monomer is of the following formula: X * wherein X and X 1 are the same and R 1 , R 2 , R 3 , and R 4 are as defined previously.
• RMC 14 monomers include dimethylsiloxane-diphenylsiloxane copolymer endcapped with a vinyl dimethylsilane group; dimethylsiloxane-methy Iphenylsiloxane copolymer endcapped with a methacryloxypropyl dimethylsilane group; and dimethylsiloxane endcapped with a methacryloxypropyldimethylsilane group.
• a ring-opening reaction of one or more cyclic siloxanes in the presence of triflic acid has been found to be a particularly efficient method of making one class of inventive RMC 14 monomers. Briefly, the method comprises contacting a cyclic siloxane with a compound of the formula:
• the cyclic siloxane may be a cyclic siloxane monomer, homopolymer, or copolymer. Alternatively, more than one cyclic siloxane may be used.
• a cyclic dimethylsiloxane tetramer and a cyclic methyl-phenyl siloxane trimer/tetramer are contacted with bis- methacryloxypropyltetramethyldisiloxane in the presence of triflic acid to form a dimethylsiloxane methylphenylsiloxane copolymer that is endcapped with a methacryloxylpropyldimethylsilane group, an especially preferred RMC 14 monomer.
• any refraction modulating composition may be used such as photorefractive, photo-addressable, and liquid crystal compositions
• the optical data storage elements may be fabricated with any suitable method that results in a FPMC 12 with one or more components which comprise the RMC 14 dispersed therein, and wherein the RMC 14 is capable of stimulus-induced polymerization to form a second polymer matrix 18.
• the method comprises mixing a FPMC 12 composition with a RMC 14 to form a reaction mixture; placing the reaction mixture into a mold; polymerizing the FPMC 12 composition to form said optical data storage element 10; and, removing the optical data storage element 10 from the mold.
• the type of mold that is used will depend on the optical data storage element being made. For example, if the optical data storage element 10 is a prism, as shown in Figures 2a to 2d, then a mold in the shape of a prism is used. Similarly, if the optical data storage element 10 is a disk, as shown in Figures la to Id, then a disk mold is used and so forth.
• the FPMC 12 composition comprises one or more monomers for forming the FPMC 12 and optionally includes any number of formulation auxiliaries that either modulate the polymerization reaction or improve any property (whether or not related to the optical characteristic) of the optical data storage element 10.
• the RMC 14 comprises one or more components that together are capable of stimulus-induced polymerization to form the second polymer matrix 18. Because flexible and foldable optical data storage elements generally permit more durable elements, it is preferred that both the FPMC 12 composition and the RMC 14 include one or more silicone-based or low T g acrylic monomers.
• the optical data storage composition 10 can be designed into any suitable conventional data storage device. For example, one data storage device 50 is shown schematically in Figure 12. In this embodimentthe optical data storage device 50 comprises abase material 52 embossed with a tracking layer 54 which serves to assist in the tracking process and provides tracking information.
• any suitable material can be utilized for such a base material and tracking layer 54, such as, for example a metallised Mylar sheet or even a separate optical data composition layer on a plastic substrate.
• the size and format of the tracks can take any suitable format, such as, for example, in one embodiment the tracks are ANSI and ISO compliant continuous composite format standards.
• a suitable thickness for such a layer is about 30 ⁇ m.
• the data storage composition 10 is then coated onto the tracking layer 54.
• the data storage composition 10 is coated over the tracking layer 54 in a thickness suitable to store single or multiple optical patterns at varying depths.
• a typical thickness for such a layer is about 50 ⁇ m, however any thickness can be used, for example thicker films might be used to allow for the input of larger three-dimensional holographic data.
• a transparent protective outer layer 56 is then coated over the data storage composition 10 to provide durability. Any other conventional coating layer may be added to the data storage device 50 described above as required by the application. For example, in case a thermal erasure process is utilized, an additional oxide layer may be necessary.
• any suitable device may be constructed such that the data storage composition 10 of the current invention can be controllably exposed to a sufficient stimulus such that data can be imprinted into the data storage composition 10 and such that the data can be reliably recovered therefrom.
• the data storage unit may be disposed between a pair of conducting electrode layers.
• the basic optical data storage device described above may be made in any suitable size such that the device will fit into appropriate data read and write apparatuses, such as, for example, a disk, cassette, optical card, CD or DVD.
• Optical properties of the optical data storage element 10 as described above can be modified, e.g., by modifying the polymerization of the RMC 14. Such modification can be performed even after data has been stored in the optical data storage element 10 so long as the final lock has not been carried out. For example, any errors in the stored data may be corrected or new data entered in a post data-write procedure.
• the stimulus-induced polymerization of the RMC forms a second polymer matrix 18 which can change the refractive index of the optical data storage element in a predictable manner, thus affecting a readable change in the optical data storage element phase contrast.
• Induction of polymerization of the RMC 14 of an optical data storage element 10 can be achieved by exposing the optical data storage element 10 to a stimulus 16.
• a method of inducing polymerization of an optical data storage element 10 having a FPMC 12 and a RMC 14 dispersed therein comprises:
• Such differential polymerization of the RMC 14 can be achieved via any suitable means of changing the intensity of the stimulus 16 spatially across the optical data storage element 10, such as, for example, by exposing only a portion of the optical data storage element 10 to the stimulus 16 via a photomask and collimated beam; or alternatively by utilizing a stimulus source capable of variable intensity across the entire area of the optical data storage elements 10, such that the optical data storage element 10 is subject to a spatially variable stimulus.
• the method of implementing the optical data storage element 10 further comprises:
• Step (c) re-exposing a portion of the optical data storage element 10 to the stimulus 16. This procedure generally will induce the further polymerization of the RMC 14 within the exposed data storage region 20. Steps (b) and (c) may be repeated any number of times until the data has been stored. The waiting period is important to establish a null point where the volume shrinkage usually seen in photo-induced polymers is overcome by macromer diffusion.
• the method may further include the step of exposing the entire optical data storage element 10 to the stimulus 16 to lock-in the desired data.
• Induction of the polymerization of the RMC in an optical data storage element 10 can also be achieved by:
• the method may include an interval of time between the exposures of the first optical data storage portion and the second optical data storage portion.
• the method may further comprise re-exposing the first optical data storage portion and/or the second optical data storage portion any number of times (with or without an interval of time between exposures) or may further comprise exposing additional portions of the optical data storage element 10 (e.g., a third optical data storage portion, a fourth optical data storage portion, etc.).
• the method may further include the step of exposing the entire optical data storage element 10 to the stimulus 16 to lock-in the desired data.
• the location of the one or more exposed portions 20 will vary depending on the amount of data being stored.
• the exposed portion 20 of the optical data storage element 10 is the center region of the optical data storage element 10 (e.g., between about 4 mm and about 5 mm in diameter).
• the one or more exposed optical data storage portions 20 may be along the optical data storage element's 10 outer rim or along a particular meridian.
• a stimulus 16 for induction of polymerization of the RMC 14 can be any appropriate coherent or incoherent light source.
• the stored data itself can be in any known high or low resolution format, such as for example where the exposed or stimulated region represents a digital "1" and the non-exposed or non-stimulated region represents a digital "0"; or where the data is stored in an analog or holographic format.
• a source of light 101 provides a beam 102 of collimated incoherent or coherent radiation, such as from a laser for example.
• the beam 102 is split into a writing beam 103 and a reference beam 104 by beamsplitter 105.
• the reference 104 and writing 103 beams interfere at the optical storage medium 10.
• a mirror 107 is normally required to redirect one of the beams 103 or 104 to the optical storage medium 10.
• a modulation can be placed on the writing beam 103 by modulator 108.
• the modulator 108 may be electrooptic or acoustooptic and may modulate one or more of the phase, amplitude and polarization of the beam 103.
• a computer 109 is typically used to control the operation of the modulator 108 in a known way so as to encode the beam 103 with desired information which is subsequently stored in the optical storage medium 10.
• the stored information is retrieved from the optical storage medium 10 by the arrangement shown in Figure 8b.
• the optical storage medium 10 is illuminated by a light source 110 with a beam 111.
• the light source 110 has a different wavelength to the writing light source 101. Since the reading and writing is occurring at different wavelengths the incident angle of the respective beams with the optical storage medium will be different and set by the Bragg relation.
• a reflected beam 112 impinges a detector 113 which supplies signals to, typically, the computer 109 for analysis to decode the encoded information.
• the information stored in the optical storage medium 10 can be erased by irradiation with a beam 114 from a light source 115 operating at a different wavelength, as depicted in Figure 8c.
• the procedure described above may be repeated as many times as necessary, such that after the write beam 104 has entered the desired data, and sufficient time has been allowed for a change in the optical properties of the optical data storage element 10, any data aberrations could be detected by the data read beam 110 and another beam 104, whose beam characteristics depend on the second set of data may be applied. This process of write/read/re-write may be continued until the desired data is stored or until the optical data storage element 10 is photo- locked.
• any suitable light source 101, beam splitter 105, mirror 107, modulator 108, computer 109, and detector 113 may be used in the current invention such that the data can be stored within the optical data storage element 10 and the data read, analyzed and, if necessary, corrected.
• the source of light 101 for the write/read/erase cycles could be any suitable light source, such as, for example, a UV light for high resolution data and IR light for low resolution data, or a coherent or incoherent visible light source, such as, a frequency doubled diode laser, a diode laser, or a helium neon laser.
• the computer and control means may conveniently be embodied in a personal computer.
• the approximate power densities required and achievable are 5-10 mW/cm 2 at 490 nm for writing, 5 mW/cm 2 at 780 nm for reading and 10 mW/cm 2 at 635 nm for erasing.
• erasure may be effected thermally or by an electric field. In these cases the application of the thermal or electric energy is controlled by the control means.
• the choice of optical, thermal or electric erasure is dependent on the storage medium of the optical storage means.
• any conventional optical data storage system can be utilized with the current data storage composition.
• a holographic data storage system 120 using Fourier hologram recordings could be utilized, as depicted schematically in Figure 9.
• a collimated laser beam 121 is directed through a spatial light modulator (SLM) 122 which impresses into the beam 121 the desired optical data 123 to be stored in the system.
• the spatially modulated output 123 of the SLM 122 is directed towards a positive lens 124.
• the SLM 122 is located at a front focal plane of the lens 124, while the optical data storage element 10, is located at a back focal plane 125.
• the modulated beam 121 After passing through the lens 124 and arriving at the optical data storage element 10, the modulated beam 121 generates the spatial Fourier transform of the original data 123 (see, for example, J. W. Goodman, Introduction to Fourier Optics, McGraw-Hill, 1968, incorporated herein by reference).
• a volume hologram is formed in the data storage device 10 by the interference of the modulated beam 121 with a reference laser beam 126 directed orthogonal to the write beam 121 and into the optical data storage element 10.
• the original signal can be retrieved by directing the reference beam 126 into the data storage element 10.
• the reconstructed beam 127 initially contains the transformed data not the original data.
• the reconstructed beam 127 must be focused by a lens 128, referred to hereafter as a readout lens.
• the readout lens 128 focuses the beam 127 on the surface of a spatial light detector 129, most commonly a charge coupled device (CCD). The resulting image is that of the original data and is consequently recovered by the detector 129.
• CCD charge coupled device
• a 4-focal length (4-f) Fourier holography arrangement has traditionally been used for holographic data storage any suitable arrangement may be utilized.
• a spatial light modulator 122 is placed at the front focal plane of a first lens 124 and the optical data storage element 10 is placed at the back focal plane 125 (the Fourier plane) of the first lens 124.
• a second lens 128 is placed after the medium at a distance from the first lens 124 equal to the sum of the focal lengths of the first 124 and second lens 128, and a detector array 129 is placed at the back focal plane of the second lens 128.
• Each pixel imaged on the detector array 129 is recorded throughout the optical data storage element 10.
• the device 120 is therefore less susceptible to error than a device which records data only at an image plane.
• the usual holographic data recording process involves the interference of two light beams on the data storage composition 10. It is accomplished by combining an image-bearing light beam and a reference beam in the data storage composition 10. The variation in intensity in the resulting interference pattern causes the complex index of refraction to be modulated throughout the volume of the medium.
• Figures 10a to lOd schematically illustrate the operation of a holographic data storage system according to that shown in Figure 9. During operation two beams, a data beam 121 and a reference beam 126 converge at a focal plane 125 creating a static interference pattern corresponding to the data 123, as shown in Figure 10a.
• the data storage device 10 containing the data storage composition is placed in the center of the interference pattern 123, as shown in Figure 10b, such that the data 123 pattern is imprinted on the data storage composition 10 in the form of a change in refractivity, absorption, or thickness of the material 123', as shown in Figure 10c.
• To read the data light from the reference beam 126 is directed at the surface of the composition 10 and the beam 126 interacts with the pattern 123' to generate a reconstructed data beam 127 which can then be detected, processed and reported to a user, as shown in Figure 1 Od.
• any suitable holograph can be created, such as, for example, a reflective or volume hologram.
• Suitable optical data storage materials comprising various amounts of (a) poly- dimethylsiloxane endcapped with diacetoxymethylsilane (“PDMS”) (36000 g/mol), (b) dimethylsiloxane-diphenylsiloxane copolymer endcapped with vinyl-dimethyl silane (“DMDPS”) (15,500 g/mol), and (c) a UV-photoinitiator, 2,2-dimethoxy-2-phenylacetophenone (“DMPA”) as shown by Table 1 were made and tested.
• PDMS poly- dimethylsiloxane endcapped with diacetoxymethylsilane
• DDPS dimethylsiloxane-diphenylsiloxane copolymer endcapped with vinyl-dimethyl silane
• DMPA 2,2-dimethoxy-2-phenylacetophenone
• the prisms are ⁇ 5 cm long and the dimensions of the three sides are ⁇ 8 mm each.
• the PDMS in the prisms was moisture cured and stored in the dark at room temperature for a period of 7 days to ensure that the resulting FPMC was non-tacky, clear, and transparent.
• the amount of photoinitiator (1.5 wt %) was based on prior experiments with fixed RMC monomer content of 25% in which the photoinitiator content was varied. Maximal refractive index modulation was observed for compositions containing 1.5 wt% and 2 wt % photoinitiator while saturation in refractive index occurred at 5 wt%.
• these RMC monomers of molecular weights 1000 to 4000 g/mol with 3- 6.2 mole % phenyl content are completely miscible, biocompatible, and form optically clear prisms and disks when incorporated in the silicone matrix.
• RMC monomers with high phenyl content (4-6 mole %) and low molecular weight (1000-4000 g/mol) resulted in increases in refractive index change of 2.5 times and increases in speeds of diffusion of 3.5 to 5.0 times compared to the RMC monomer used in Table 1 (dimethylsiloxane-diphenylsiloxane copolymer endcapped with vinyldimethyl silane (“DMDPS”) (3-3.5 mole % diphenyl content, 15500 g/mol).
• DDPS dimethylsiloxane-diphenylsiloxane copolymer endcapped with vinyldimethyl silane
• RMC monomers were used to make optical elements comprising: (a) poly- dimethylsiloxane endcapped with diacetoxymethylsilane (“PDMS”) (36000 g/mol), (b) dimethylsiloxane methylphenylsiloxane copolymer that is endcapped with a methacryloxylpropyldimethylsilane group, and (c) 2,2-dimethoxy-2-phenylacetophenone ("DMPA”).
• component (a) is the monomer that forms the FPMC and components (b) and (c) comprise the RMC.
• a lense shaped disk mold was designed according to well-accepted standards. See e.g., U.S. Patent Nos. 5,762,836; 5,141,678; and 5,213,825. Briefly, the mold is built around two plano-concave surfaces possessing radii of curvatures of -6.46 mm and/or -12.92 mm, respectively. The resulting lense disks are 6.35 mm in diameter and possess a thickness ranging from 0.64 mm, 0.98 mm, or 1.32 mm depending upon the combination of concave surfaces used.
• disks with pre-irradiation powers of 10.51 D (62.09 D in air), 15.75 D (92.44 in air), and 20.95 D ( 121.46 D in air) were fabricated.
• Three test lense disks were fabricated with 30 and 10 wt% of RMC monomers B and D incorporated in 60 wt% of the PDMS matrix. After moisture curing of PDMS to form the FPMC, the presence of any free RMC monomer in the aqueous solution was analyzed as follows. Two out of three disks were irradiated three times for a period of 2 minutes using 340 nm light, while the third was not irradiated at all. One of the irradiated disks was then locked by exposing the entire disk matrix to radiation. All three disks were mechanically shaken for 3 days in 1.0 M NaCl solution. The NaCl solutions were then extracted by hexane and analyzed by ! H-NMR.
• This disk was exposed to 2.14 mW/cm 2 of 325 nm light from a He:Cd laser for four minutes after placing a 0.5 mm width astigmatism mask 23° clockwise from vertical over the lens.
• the first disk was then photolocked three hours after the initial irradiation by exposure to a low pressure Hg lamp for 8 minutes.
• the second disk was composed of 30 and 10 wt % monomers B and D incorporated in 60 wt% of the PDMS matrix.
• This disk was exposed to 3.43 mW/cm 2 of 340 nm light from a Xe:Hg arc lamp after placing a 1 mm diameter photomask over the central portion of the disk.
• the second disk was not photolocked.
• the third disk was fabricated with 30 and 10 wt% monomers E and F incorporated in 60 wt% of the PDMS matrix. This disk was exposed to 2.14 mW/cm 2 of 325 nm light from a He:Cd laser for four minutes after placing a 1.0 mm diameter photomask over the central portion of the disk. The third disk was then photolocked three hours after the initial irradiation by exposure to a low pressure Hg lamp for 8 minutes. The fourth disk was fabricated with 30 and 10 wt% monomers E and F incorporated in 60 wt% of the PDMS matrix. The fourth disk was not irradiated. The four lense disks were placed individually into 5 ml of doubly distilled water.
• dish washing detergent a surfactant
• the disks were kept in their respective solutions for 83 days at room temperature. After this time, the lenses, in their respective solutions, were placed into an oven maintained at 37 °C for 78 days.
• Each of the aqueous solutions were then extracted three times using approximately 5 ml of hexane. All hexane extracts from each lens solution were combined, dried over anhydrous sodium sulfate (N- ⁇ SO ⁇ , and allowed to evaporate to dryness.
• Each of the four vials was then extracted with THF, spotted onto a dihydroxy benzoic acid matrix, and analyzed by MALDI-TOF. For comparison, each of the monomers and PDMS matrix were run in their pure form. Comparison of the four extracted lens samples and the pure components showed no presence of any of the monomers or matrix indicating that monomer and matrix were not leaching out of the disks.
• the inventive formulations were molded into prisms 26 for irradiation and characterization, as shown in Figures 2a to 2d.
• the prisms 26 were fabricated by mixing and pouring (a) 90-60 wt% of high M n PDMS 12 (FPMC), (b) 10-40 wt% of RMC 14 monomers in Table 2, and (c) 0.75 wt% (with respect to the RMC monomers) of the photoinitiator DMPA into glass molds in the form of prisms 5.0 cm long and 8.0 mm on each side.
• FIGS. 2a to 2d illustrate the prism irradiation procedure. Two of the long sides of each prism 26 were covered by a black background while the third was covered by a photomask 28 made of an aluminum plate 30 with rectangular windows 32 (2.5 mm x 10 mm), as shown in Figure 2b. Each prism 26 was exposed to 3.4 mW/cm 2 of collimated 340 nm light 16 (peak absorption of the photoinitiator) from a 1000 W Xe:Hg arc lamp for various time periods.
• the prisms 26 with the photomask 28 were subject to both (i) continuous irradiation - one-time exposure for a known time period, and (ii) "staccato" irradiation - three shorter exposures with long intervals between them.
• continuous irradiation the refractive index contrast is dependent on the crosslinking density and the mole % phenyl groups, while in the interrupted irradiation; RMC 14 monomer diffusion and further crosslinking also play an important role.
• staccato irradiation the RMC 14 monomer polymerization depends on the rate of propagation during each exposure and the extent of interdiffusion of free RMC 14 monomer during the intervals between exposures.
• Typical values for the diffusion coefficient of oligomers (similar to the 1000 g/mole RMC 14 monomers used in the practice of the present invention) in a silicone matrix are on the order of 10 "6 to 10 "7 cm 2 /s.
• the inventive RMC 14 monomers require approximately 2.8 to 28 hours to diffuse 1 mm (roughly the half width of the irradiated bands).
• the prisms 26 were irradiated without the photomask (thus exposing the entire matrix) for 6 minutes using a medium pressure mercury-arc lamp, as shown in Figure 2d. This polymerized the remaining silicone RMC 14 monomers and thus "locked" the refractive index of the prism in place.
• Inventive prisms 26 fabricated from RMC 14 monomers described by Table 2 were masked and initially exposed for 0.5, 1, 2, 5, and 10 minutes using 3.4 mW/cm 2 of the 340 nm line from a 1000 W Xe:Hg arc lamp, as shown schematically in Figures 2a to 2d.
• the exposed regions 20 of the prisms 26 were marked, the mask 28 detached and the refractive index changes measured.
• the refractive index modulation of the prisms 26 was measured by observing the deflection of a sheet of laser light passed through the prism 26.
• the difference in deflection of the beam passing through the exposed 20 and unexposed 22 regions was used to quantify the refractive index change (Dn) and the percentage change in the refractive index (% Dn).
• the prisms 26 were remasked with the windows 32 overlapping with the previously exposed regions 20 and irradiated a second time for 0.5, 1 , 2, and 5 minutes (total time thus equaled 1, 2, 4, and 10 minutes respectively).
• the masks 28 were detached and the refractive index changes measured.
• the prisms were exposed a third time for 0.5, 1, and 2 minutes (total time thus equaled 1.5, 3, and 6 minutes) and the refractive index changes were measured.
• the % Dn increased with exposure time for each prism 26 after each exposure resulting in prototypical dose response curves. Based upon these results, adequate RMC 14 monomer diffusion appears to occur in about 3 hours for 1000 g/mole RMC 14 monomer.
• RMC monomers (B-F) except for RMC monomer A resulted in optically clear and transparent prisms before and after their respective exposures.
• the largest % Dn for RMC monomers B, C, and D at 40 wt% incorporation into 60 wt% FPMC were 0.52%, 0.63% and 0.30% respectively which corresponded to 6 minutes of total exposure (three exposures of 2 minutes each separated by 3 hour intervals for RMC monomer B and 3 days for RMC monomers C and D).
• the prism fabricated from RMC monomer A (also at 40 wt% incorporation into 60 wt% FPMC and 6 minutes of total exposure - three exposures of 2 minutes each separated by 3 hour intervals) turned somewhat cloudy.
• the RMC monomer A were used to fabricate a transparent optical data storage device, then the RMC must include less than 40 wt% of RMC monomer A or the % Dn must be kept below the point where the optical clarity of the material is compromised.
• Talbot interferometry and the Ronchi test were used to qualitatively and quantitatively measure any optical aberrations (primary spherical, coma, astigmatism, field curvature, and distortion) present in pre- and post-irradiated lense disks 10 as well as quantifying changes in power upon photopolymerization.
• optical aberrations primary spherical, coma, astigmatism, field curvature, and distortion
• the test data storage element 10 is positioned between the two Ronchi rulings with the second grating placed outside the focus of the element and rotated at a known angle, q, with respect to the first grating.
• a second Moire fringe pattern is constructed by axial displacement of the second Ronchi ruling along the optic axis a known distance, d, from the test element. Displacement of the second grating allows the autoimage of the first Ronchi ruling to increase in magnification causing the observed Moire fringe pattern to rotate to a new angle, ⁇ .
• Knowledge of Moire pitch angles permits determination of the focal length of the lens (or inversely its power) through the expression:
• Moire fringe patterns of one of the inventive, pre-irradiated data storage elements 60 wt% PDMS, 30 wt% RMC monomer B, 10 wt% RMC monomer D, and 0.75% DMPA relative to the two RMC monomers measured in air is presented in Figures 3a and 3b.
• Each of the Moire fringes was fitted with a least squares fitting algorithm specifically designed for the processing of Moire patterns.
• the angle between the two Ronchi rulings was set at 12°
• the displacement between the second Ronchi ruling between the first and second Moire fringe patterns was 4.92 mm
• Optical aberrations of the inventive elements were monitored using the "Ronchi Test” which involves removing the second Ronchi ruling from the Talbot interferometer and observing the magnified autoimage of the first Ronchi ruling after passage through the test element.
• the aberrations of the test elements manifest themselves by the geometric distortion of the fringe system (produced by the Ronchi ruling) when viewed in the image plane. Knowledge of the distorted image reveals the aberration of the element.
• inventive fabricated elements both pre and post irradiation treatments
• Figure 4 is an illustrative example of a Ronchigram of an inventive, pre-irradiated element that was fabricated from 60 wt% PDMS, 30 wt% RMC monomer B, 10 wt% RMC monomer D, and 0.75% of DMPA relative to the 2 RMC monomers.
• the use of a single Ronchi ruling may also be used to measure the degree of convergence of a refracted wavefront (i.e., the power).
• the test element is placed in contact with the first Ronchi ruling, collimated light is brought incident upon the Ronchi ruling, and the element and the magnified autoimage is projected onto an observation screen.
• Magnification of the autoimage enables measurement of the curvature of the refracted wavefront by measuring the spatial frequency of the projected fringe pattern.
• P v is the power of the element is expressed in diopters
• L is the distance from the lens to the observing plane
• d s is the magnified fringe spacing of the first Ronchi ruling
• d is the original grating spacing
• the data storage element 10 was fitted with a 1 mm diameter photomask 28 and exposed to 3.4 mW/cm 2 of 340 nm collimated light 16 from a 1000 W Xe:Hg arc lamp for two minutes, as shown in Figure 5a.
• the irradiated data storage element 10 was then placed in the dark for three hours to permit polymerization and RMC 14 monomer diffusion, as shown in Figure 5b.
• Figure 6b (right interferogram) is the Ronchi interferogram of the element 10 taken six days after irradiation.
• the most obvious feature between the two interference patterns is the dramatic increase in the fringe spacing 38, which is indicative of an increase in the refractive power of the element 10.
• Measurement of the fringe spacings 38 indicates an increase of approximately +38 diopters in air (f » 7.5 mm). Indicating that this mechanism might be utilized in the system of the present invention.
• Inventive data storage elements 10 using non-phenyl containing RMC monomers 14 were fabricated to further study the swelling from the formation of the second polymer matrix 18.
• An illustrative example of such a data storage element 10 was fabricated from 60 wt% PDMS, 30 wt% RMC monomer E, 10 wt% RMC monomer F, and 0.75% DMPA relative to the two RMC monomers.
• the pre-irradiation focal length of the resulting element 10 was 10.76 mm ⁇ 0.25 mm (92.94 ⁇ 2.21 D).
• the light source 16 was a 325 nm laser line from a He:Cd laser.
• a 1 mm diameter photomask 28 was placed over the element 10 and exposed to a collimated flux 16 of 2.14 mW/cm 2 at 325 nm for a period of two minutes.
• the element 10 was then placed in the dark for three hours.
• Experimental measurements indicated that the focal length of the element 10 changed from 10.76 mm ⁇ 0.25 mm (92.94 D ⁇ 2.21 D) to 8.07 mm ⁇ 0.74 mm (123.92 D ⁇ 10.59 D) or a dioptric change of + 30.98 D ⁇ 10.82 D in air.
• the amount of irradiation required to induce these changes is only 0.257 J/cm 2 .
• inventive data storage elements 10 were monitored to show that handling under ambient light conditions does not produce any unwanted changes in element.
• a 1 mm open diameter photomask was placed over the central region of an inventive element (containing 60 wt% PDMS, 30 wt% RMC monomer E, 10 wt% RMC monomer F, and 0.75 wt% DMPA relative to the two RMC monomers), exposed to continuous room light for a period of 96 hours, and the spatial frequency of the Ronchi patterns as well as the Moire fringe angles were monitored every 24 hours.
• the focal length measured in the air of the optical element immediately after removal from the optical element mold is 10.87 ⁇ 0.23 mm (92.00 D ⁇ 1.98 D) and after 96 hours of exposure to ambient room light is 10.74 mm ⁇ 0.25 mm (93.11 D ⁇ 2.22 D).
• ambient light does not induce any unwanted change in optical properties.
• a comparison of the resulting Ronchi patterns showed no change in spatial frequency or quality of the interference pattern, confirming that exposure to room light does not affect the power or quality of the inventive data storage elements 10.
• the IOL was refitted with a 1 mm diameter photomask and exposed a second time to 2.14 mW/cm 2 of the 325 nm laser line for two minutes. As before, no observable change in fringe space or in optical quality of the data storage element was observed.
• the inventive data storage element (containing 60 wt% PDMS, 30 wt% RMC monomer E, 10 wt% RMC monomer F, and 0.75 wt% DMPA relative to the two RMC monomers) was subject to three 2 minute irradiations over its entire area that was separated by a 3 hour interval using 2.14 mW/cm 2 of the 325 nm laser line from a He:Cd laser.
• Ronchigrams and Moire fringe patterns were taken prior to and after each subsequent irradiation.
• the Moire fringe patterns taken of the inventive data storage element in air immediately after removal from the mold and after the third 2 minute irradiation indicate a focal length of 10.50 mm ⁇ 0.39 mm (95.24 D ⁇ 3.69 D) and 10.12 mm ⁇ 0.39 mm (93.28 D ⁇ 3.53D) respectively. These measurements indicate that photolocking a previously unexposed element does not induce unwanted changes in optical properties. In addition, no discernable change in fringe spacing or quality of the Ronchi fringes was detected indicating that the refractive power had not changed due to the lock-in.
• Phase contrast variation of a composition comprising a refraction modulating composition
• DMPA 2,2-dimethoxy-2- phenylacetophenone
• the irradiation was carried out using the 325 nm line of a He:Cd laser.
• the beam emanating from the laser was focused down on to a 50 ⁇ m pinhole by a 75 mm focusing lens.
• a 125 mm lens was placed at a focal distance away from the pinhole to collimate the light producing a beam diameter of approximately 1.6 mm. Collimation of the beam was insured by monitoring the tilt angle of the fringes formed from a shearing plate interferometer placed in the beam.
• a 5000 lines/inch (a period of ⁇ 5 ⁇ m) ruled grating was placed over the top surface of the sandwiched film and the photo-induced refractive composition was exposed to the Talbot autoimage of the grating using 6.57 mW/cm 2 of collimated 325 nm light for 90 seconds.
• Figure 11 shows a microscope picture of the film after irradiation through the 5000 lines/inch mask. The magnification of the picture is approximately 125X. The alternating dark and light stripes running through the picture have a period of approximately 5 ⁇ m as determined by a calibrated microscope target. Therefore, the photoresponsive materials possess high spatial phase contrast.
• the composition of the current invention represents a digital " 1 " and the non-exposed or non-stimulated region represents a digital "0".
• a second experiment shown in Figure 7, two sets of data were stored on a single photopolymer disk. First a 5000 lines/inch (a period of ⁇ 5 ⁇ m) ruled grating was placed over the top surface of the sandwiched film and then a photomask having the words "CALTECH” and "CVI” was placed atop that. Then the photo-induced refractive composition was exposed to the Talbot autoimage of the grating and photomask using 6.57 mW/cm 2 of collimated 325 nm light for 90 seconds.
• both the Ronchi rule and the words were inscribed on the photopolymer disk of the composition according to the present invention, this shows that patterns of any shape can be utilized to inscribe both high and low resolution data on the same disk of material simultaneously.
• the incident light was orthogonal to the plane of the optical element (slab or lens) and data, in the form of the Ronchi rule was stored at only a single angle.
• data can be stored in the data storage composition 10 of the current invention more than once and at different angles. Such a multiple storage can be performed by tilting the slab by a certain angle and exposing it to UV-light through the ronchi ruling.

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• Polymerisation Methods In General (AREA)
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• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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• 2001
  • 2001-05-10 BR BR0110937-5A patent/BR0110937A/pt not_active Application Discontinuation
  • 2001-05-10 CA CA002408244A patent/CA2408244A1/en not_active Abandoned
  • 2001-05-10 JP JP2001583512A patent/JP2003533718A/ja active Pending
  • 2001-05-10 MX MXPA02011035A patent/MXPA02011035A/es unknown
  • 2001-05-10 US US09/853,885 patent/US20020042004A1/en not_active Abandoned
  • 2001-05-10 WO PCT/US2001/015419 patent/WO2001086647A2/en not_active Ceased
  • 2001-05-10 CN CN01812101A patent/CN1440551A/zh active Pending
  • 2001-05-10 AU AU2001259755A patent/AU2001259755A1/en not_active Abandoned
  • 2001-05-10 EP EP01933324A patent/EP1281176A2/de not_active Withdrawn

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